Instrument valve limit
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Yesterday, after a valve equipped with a controller had been in operation for 30 days, it started to leak internally; it couldn’t be shut off at the site. The controller was used to adjust the limit settings, and as a result, the leakage stopped. Since the valve didn’t leak at the beginning of its operation, this indicated that its limit settings were correct and that its spherical seal was in good condition. The sudden appearance of leakage later on was likely due to wear and tear on the valve. What’s unclear is why adjusting the limit settings on the valve’s controller could prevent leakage – what is the reason for this? I hope fellow sailors can give some guidance
The sealed areas with erosion damage should be staggered.
The limit switch may also break for no reason
The function of the limit switch is to provide a signal indicating that the system has reached its proper position. By adjusting the limit switch backward, it is possible to move the valve further, which in turn allows the valve stem to be pressed more tightly.
I have another question for everyone. Generally, ball valves don’t leak; at the beginning, the seal between the ball and the valve body should be perfect. Adjusting the valve’s limits indicates that there is still some margin left, right? 2. The ball valve operates properly when switched on and off, so why does leakage occur?
After adjusting the limit, there is no more leakage, which indicates that the gap between the sealing surfaces increased during operation; by adjusting the limit to reduce this gap, leakage is prevented. This is also a method for resolving the issue.
Is there usually a gap between ball valves during operation?
I would like to ask fellow sailors: do valves generally have some margin even without limit settings?
The limit switch of the control valve is activated because the gap in this valve has increased. There are many reasons for this, such as wear caused by the medium, prolonged operation at a low valve position, and the effects of cavitation on the valve. What you have here is only a static consideration of the issue, without any dynamic considerations.
If there is an effect, it means there is a gap; and if there is a gap, it indicates that the previous limits have changed. The value of the limit is actually uncertain
The questioner didn’t clearly specify what type of valve it is – a valve with angular motion. If it’s a valve with linear sealing like a ball valve, the sealing surface is in good condition at first; as the valve is opened and closed or operated, the sealing surface gets damaged, but other parts remain intact, and slightly adjusting the angle can still ensure sealing